Cross-Section Stratigraphy Model

Frequently, the geologist does the initial logging of the well and the hydrologist or hydrogeologist interprets these logs to come up with a coarser aggregation that lumps together the fine-scaled designations applied by the geologist. This interpreted geology is what is referred to as Stratigraphy in operation of EnviroInsite and what is plotted as Fence Diagrams or Geologic Models.Geologic models may also be plotted on cross sections as in the following image. These are created from the cross-section view window by selecting Stratigraphy -> Model. Stratigraphy models on the cross-section are drawn based on the records in the Stratigraphy table. Fence diagrams and 3d geologic models are generated by interpolation of the contact elevation to the defining polygon.

The resulting model may be edited manually selecting individual points on the contact surface and then dragging the points upward or downward. In order to preserve these manual edits you may select the Detach from Data option of the Stratigraphy plot object.

Click here to view a training video on modeling of stratigraphy

Query

The query dialog box is similar to that used in other parts of the application. In this case however, you need to select the stratigraphic units to be plotted. Select units from the list box on the left and hit add to include them in the list of units to be plotted. The units should be in order from top-down of their appearance in the physical model. That is the uppermost units in the real world should be added to the list first followed by the other units.

Format

Interpolation

This tab allows the user to select the interpolation scheme and the parameters of the interpolation method. Selection of interpolation parameters is critical for generation contours that accurately reflect the field data and our expectations of values between the data points. The default parameters are generally adequate, although some improvement can be anticipated through trial and error. There is no single, objectively optimal set of interpolation parameters. Different methods and parameters work best for different data sets.

Search Radius - The cutoff distance establishes the maximum distance from the interpolated point for which a measured value will be used in the interpolation function. Used by both kriging and inverse distance routines.

Default Value - This is the default value for points within the grid that are interpolated because they lie outside the search radius or outside the user-defined polygon from the grid tab

Use Default Value - Specify whether the default value will be used or that the non-interpolated nodes will not be contoured.

Inverse Distance Parameters

Vertical scale factor - The vertical distances between the interpolated and measured point are multiplied by the vertical scale factor prior to the computation of the distance used in the interpolation function. This accounts for the relatively low persistence of data fields in the vertical direction. The vertical scale factor is generally set to values greater than one for horizontal correlation distances exceeding those in the vertical direction.

Exponent - The power value used in the inverse distance interpolation routine.

Smooth Distance - Distance added to every calculation of grid point - measured value distance to encourage smoothness of interpolated result.

Kriging Parameters

The kriging routines are from the kt3d routine of the Geostatistical Software Library (GSLIB) authored by Clayton Deutsch and Andre Journel (www.gslib.com).

Model - Select from the spherical, exponential, gaussian, power and hole variogram models using conventions of GSLIB. The variogram functions are shown on the dialog box (see figure above).

Sill - variogram model sill or c value from the variogram models

Nugget - local scale variability

a max - maximum horizontal range

a min - minimum horizontal range

a vert - vertical range

angle - rotation angle in degrees clockwise about 12 o'clock of the axis defining the direction of maximum horizontal range